The present invention relates to a triggering circuit for extracorporeal disintegration of kidney stones.
Kidney stones, and also naturally occuring stones in the bladder and the ureter can be exquisitely painful, and often require surgical relief. Excision or destruction of stones in the bladder and sometimes in the ureter can be relatively easily accomplished but removal of stones from the kidney is a major procedure.
Removal of stones from the kidney is a very serious and traumatic surgical procedure. A large incision is made in the body. The kidney is essentially removed from the body and cut open. The stone or stones are then removed, whereupon the kidney is sutured and returned to the body, with the body then being sutured.
Chemotherapy is available as a non-invasive therapy for uric acid stones. In this therapy the urine is alkalized. The existing stone thus is dissolved over a substantial period of time, and in most cases the patient can be cured before his condition becomes acute. However, the patient's condition is often already acute when the stone is discovered, and immediate surgery is imperative. Attempts at chemical dissolution of other types of stones have not been successful.
There are procedures for removing stones from the bladder which do not require cutting of the body. They are, however, invasive procedures in that the necessary devices are inserted through the urethra. In one of these procedures an electrohydraulic impulse is provided. A high energy capacitor is discharged by means of a coaxial electrode within the bladder, whereby a spark jumps between two poles of said electrode, establishing a hydrodynamic wave which destroys the concretion upon contact. The electrode thus must be in close proximity to the stone and a cystoscope having an optical telescope is utilized to visualize the spark generating electrodes.
As an alternative, ultrasonic waves on the order of 27 KHz. are used to disintegrate bladder stones. An optical device and an ultrasound converter are carried by a hollow steel probe which is inserted through the urethra. High frequency electrical energy is transformed into mechanical energy by an ultrasound converter and carried by the hollow steel probe which must be in contact with the bladder stone.
With both electrohydraulic impulses and ultrasonic disintegration of bladder stones it has been necessary for the energy source to be very close to or to effect physical contact with the stone. Such procedures are transuretheral and are routine for bladder stones. Ureteral stones and kidney stones recently have been fragmented by such techniques percutaneously. Such procedures are invasive, but do not involve major cutting of the body.
The percutaneous approach to ureteral and kidney stones has avoided the massive surgery outlined heretofore. A needle is inserted through the skin to the renal pelvis, the collecting area of the kidney. The needle is hollow and a guide wire is inserted through the needle into the kidney. The needle is then removed, and successively larger tubes are run in over the guide wire, leading up finally to a tube 8 mm in diameter. Viewing and stone cracking apparatus then are inserted through this tube to crack or disintegrate the stone. The approach is still invasive, and traumatic to the patient.
One approach has been made on an experimental basis of non-invasive breaking-up or disintegration of kidney stones in the body. Such non-invasive disintegration of kidney stones is disclosed in U.S. Pat. Nos. 3,942,531 to Hoff et al and 4,311,147 to Hausler. The first of these patents is exemplified in a machine commercially available in the Federal Republic of Germany from Dornier System GmbH. A few of the Dornier machines are now in the United States. Such machines are quite large since they require the patient to be immersed in a tub of water in a crouched, face-up position. Two dimensional X-ray procedures are utilized to determine the position of the stone by moving the patient. The machine includes an underwater spark gap shock wave generator which lies outside of the patient's body and at the first focal point of an ellipsoid. The patient is moved around in the water bath by servo mechanisms utilizing the two dimensional X-ray technique until the kidney stone is positioned at the second focal point of the ellipsoid. Since X-rays are used only radio opaque stones can be located. The shock wave is then generated, and passes through the water bath and through the patient's body to convey the energy to the kidney stone. The Dornier machine requires a 40 square meter room 3 meters in height. The machine base is six meters by one meter. The present cost of the machine, which may be expected to rise with inflation, is two million dollars, plus 10% of the price of the machine each year for a service contract. The service contract includes the cost of a technician who must be on hand at all times when the machine is in operation. It is contra-indicated if the ureter is blocked, since the material must pass out through the ureter. It is also unsuccessful with radio transparent or translucent stones, since they cannot be located by X-ray techniques. It must be emphasized that precise aiming of an external shock wave is necessary since energy focused into an air or gas pocket in the body can cause damage to interface tissue.
It has been found that if the shock wave is applied to the body other than during or immediately after ventricular contraction a few fibrillations of the heart have been produced. Such fibrillation obviously is to be avoided.